Cancer is one of the top three causes of death in the world. Of all cancers, more than 85% have epithelial origin, meaning that they pertain close to the surface. An example is the skin. Skin is composed of three primary layers: the epidermis, which provides waterproofing and serves as a barrier to infection; the dermis, which serves as a location for the appendages of skin; and the hypodermis, a subcutaneous adipose layer, which is also called the basement membrane.
Epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous epithelium with an underlying basal lamina.
In between epidermis and dermis the basal layer or Stratus basale is located consisting of a single layer of tall, simple columnar epithelial cells lying on a basement membrane. These cells undergo rapid cell division, mitosis to replenish the regular loss of skin by shedding from the surface. About 25% of the cells are melanocytes, which produce melanin that provides pigmentation for skin and hair.
The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by the basal layer. The blood vessels in the dermis provide nourishment and waste removal to its own cells as well as the basal layer of the epidermis.
The hypodermis is not part of the skin, and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves.
Apart from the skin several other epithelial cancer types exists, among others lung cancer, cervical cancer, gastrointestinal cancer, and skin cancer. The epithelial cancer development may be characterized in different stages.
In the hyperplastic stage, the morphology of cells does not change, only the number of epithelial layers, and hence the thickness of epidermis changes.
In the dysplastic stage, cells change in shape and size. Furthermore, there is clear evidence for an increase in the pre-malignant epithelial microvascular blood content in dysplasia, so-called angiogenesis, which is not typical in benign tumors in hyperplastic stage. Therefore, angiogenesis is a unique mark for malignant hyperplasia. Additionally, blood oxygen content has decreased in late dysplasia or carcinoma.
In the carcinoma in situ stage, cell morphology has changed even further and aberrant cells have spread throughout the epidermis. Finally, in the carcinoma stage, cancer cells have crossed the basal layer and may spread, or metastasize, throughout the body.
Differential Path Length Spectroscopy (DPS) (see patent application WO 2005/029051) is an optical technology for cancer detection, in cancers such as breast cancer, oral cancer, and brain cancer. It is a fiber-optic technique in which white light is delivered to the tissue by a delivery-collection (DC) fiber. Part of the light is backscattered by the turbid tissue and is measured by two fibers, i.e., the DC fiber and a collection fiber, which is glued to the DC fiber. The actual signal is the difference between the signals of the two fibers. Subtraction of the two signals reduces the presence in the signal of multiple-scattered photons, and in this way the probe depth is reduced. DPS measures tissue properties from single and multiple-scattered photons, with a constant probe depth that may be tuned by choosing a particular fiber diameter. The constant path length enables absolute measurement of blood oxygenation, blood amount, average blood vessel diameter and scattering, all of which are changed when tissue becomes cancerous. A disadvantage of DPS is that it is not well suited for early detection of tissue aberrations, because three out of four parameters only change significantly when cancer has already developed. For example, in the hyperplastic stage, blood oxygenation, amount of blood, and the average vessel diameter will not have changed yet. Only the scattering is influenced in the hyperplastic stage. However, the DPS modality is not very sensitive to a change in this parameter.
Another known technology for cancer detection is Polarized Light Scattering Spectroscopy (LSS) (see V. Backman et al., IEEE J. Selected Topics Quantum Electron., Vol. 5, No 4, July/August 1999, p. 1019). The principle of LSS is that linearly polarized light from a white light source is incident on the tissue to be investigated. Diffusely scattered light is detected and the intensity of both polarization components is measured. The principle of the technique is based on the fact that photons that scatter once or twice will mostly retain their polarization, whereas multiple scattered photons will lose their polarization. Hence, by subtracting the two measured light intensities I⊥ and I∥ the contribution of the multiple scattered photons will cancel. LSS spectra of tissue may be modeled with Mie theory and by fitting of experimental spectra it is possible to obtain three parameters: the average cell size, standard deviation in cell size, and the refractive index of the tissue. It has been shown that these three parameters are different for malignant tissue and may be used for cancer detection. A disadvantage of LSS is that it is not sensitive to detection of early stages of cancerous tissue as the maximum imaging depth or probe depth is limited such that it is only possible to image a limited part of the epidermis. This makes LSS insensitive to the hyperplastic stage as the layer thickening of the epidermis in the hyperplastic stage may not be measured. Furthermore, due to the limited probe depth of LSS no scattering information is obtained from below the epithelial layer, which is important in differentiating between carcinoma in situ and carcinoma.
Accordingly, both the DPS modality and LSS modality have disadvantages regarding the suitability in detecting early stages of cancer development. Hence, an improved system, computer-readable medium, method, and use for early cancer diagnosis or staging would be advantageous.